Juice is a battery replacement kit that uses a pretty nifty set of AA, AAA, A23 and CR2032 inserts to inject the required regulated power where a battery or two would normally be required.
Power can be supplied via the micro USB connector, or any other power supply that can be clipped or screwed on to the body of the Juice.
All the structural parts punch out from the classy PCB like a model plane kit;-) The box folds up and doubles as a “Juice box”.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub